Every kind of a car body control system or engine control system has been developed to clear all sorts of regulations of the car and to give a good ride in the car. There is an acceleration sensor or a semiconductor pressure sensor required for these systems.
Since the acceleration sensor used for a car, for instance, has to detect acceleration which is comparatively small and has considerably long fluctuation cycles, a semiconductor electrostatic capacitance type acceleration sensor or a semiconductor strain gage type acceleration sensor has been used mainly.
However, these conventional sensors have characteristics which fluctuate after they are manufactured. Accordingly, it is necessary to adjust the detection sensitivities and/or the zero points with a signal processing circuit. For instance, one adjusting method is that a signal processing circuit is formed by a printed circuit board, and one resistance element of an output adjustor of the printed circuit board has to be selected for obtaining an adjusted output signal of the sensor. Another adjusting method is that the signal processing circuit is formed by a hybrid integrated circuit, and one resistance element of the output adjustor of the hybrid integrated circuit has to be selected by laser trimming to obtain an adjusted output signal of the sensor.
However, the size of the conventional signal processing circuit of the sensor is large so that the cost thereof becomes high. Moreover, the wiring length between the detector and the signal processing circuit becomes long and the number of the wires is increased. As a result, a drawback that occurs in the conventional sensor is that the probability of breakage of wires becomes high due to temperature variation or acceleration.
On the other hand, it is considered that the signal processing circuit is integrated, thin film resistances are formed on the integrated circuit and the resistance is trimmed analogously using a laser to adjust the resistance value. However, in the sensor made by the above-mentioned method there occurs easily secular change at the trimmed resistance value so that the sensor lacks reliability as an acceleration sensor. In this kind of acceleration sensor, there is prior art relating to the semiconductor electrostatic capacitance type sensor disclosed on pages 395 to 398 and relating to the semiconductor strain gage type sensor disclosed on pages 399 to 402 of "Transducer '87 The 4th International Conference on Solid-State Sensors and Actuators" published on Jun. 2-5, 1987 in Tokyo, Japan.
The above-mentioned prior art has a drawback in that the variations of the sensitivity and the zero point generated at manufacturing of the detectors are not adjusted perfectly, and the size of the sensors are large; the cost thereof is high, and they lack in reliability.